1. Field of Invention
The present invention relates to illumination optical devices and projectors.
2. Description of Related Art
In the related art a so-called three-plate projector of a type separates a light flux coming from a light source device into color light beams of three RGB colors using a dichroic mirror, performs modulation using three liquid crystal panels (light modulators) on a color light beam in accordance with image information, synthesizes the resulting light flux having been subjected to modulation using a cross dichroic prism, and enlarges and projects color images via a projection lens.
Such a projector is provided with an illumination optical device 100 as shown in FIG. 8. This illumination optical device 100 includes a light source device 110, and a uniform illumination optical system 150. The light source device 110 includes a light-emitting tube (light source lamp 12) as a radiation light source, an elliptical reflector 130, and a collimator concave lens 140. Radial light beams emitted from the light source lamp 12 are reflected and emitted by the elliptical reflector 130, and then collimated by the collimator concave lens 140.
The uniform illumination optical system 150 has a function of dividing the resulting light flux reflected by the elliptical reflector 130 into a plurality of partial light fluxes, and superposing the resulting light onto an image formation region of a liquid crystal panel 41. Included therein are: a light flux dividing optical element (first lens array 160); a polarization conversion element (PBS array 180); a second lens array 170; and a condenser 190 See for example, JP-A-2000-347293, pages 12 to 13, and FIG. 14.
With such an illumination optical device 100, for the purpose of capturing every light flux coming from the light source lamp 12, each of the first lens array 160, the second lens array 170, the PBS array 180, and the condenser 190 has an effective light flux passing region being square in outer shape. One side dimension thereof is almost equalized to the diameter dimension of the reflection plane at an opening portion of the reflector 130 (hereinafter, “effective reflection plane diameter”). Note here that the “effective light flux passing region” indicates a region in which, out of light fluxes passing through these optical components, any light flux allowed to pass through the image formation region of the light modulator (to-be-illuminated region) is observed. For example, in the vicinity of the second lens array 170, the PBS array 180, and the condenser 190, observed are images (arc images) as a result of converging a plurality of partial light fluxes that have been through division by the first lens array 160. The effective light flux passing region in this case is a virtual rectangular region to completely include such converged images.